Automatic chuck



Sept. 9, 1952 o. H. BANKER 2,610,065

AUTOMATIC CHUCK Filed May,l0, 1947 2 SHEETSSHEET l "III"!!! 7IIIIIIIIIIIL 1/6 8 W ZW Patented Sept. 9, 1 952 OFFICE AUTOMATIC CHUCKOscar H. Banker, Evanston, Ill. Application May 10, 1947, Serial No.747,236

'6 Claims. (Cl. 279-23) The invention relates to. an automatic chuck fordriving rotatable elements such as tools or spindles of food and drinkmixers and other household utilities that have removable drivenelements.

The principal object of the invention is to provide a chuck of the typereferred to which has collet for increasing the grip of the collet onthe driven element, and further to associate such an improved clutchingmeans for connecting the driven element in driving relation to therotating chuck body and in this respect seeks to overcome thedisadvantages inherent in chucks of the type heretofore known. In onesuch prior chuck the clutching action between the rotating chuck bodyand driven element is dependent upon mechanism including centrifugalweights operable in response to high speed rotation of the chuck body. Achuck of this type has one important disadvantage; namely, the clutchingdevice tends to lose its grip on the driven element whenever the speedof the chuck is reduced below a certain rate, as will occur in the eventthat an extraordinary load is placed upon the driven element. Thisdisadvantage is characteristic of any chuck that depends upon high speedrotation for the efficiency of the clutching action between the chuckbody and the driven element. It is an important object of the inventionto eliminate this disadvantage by the provision of clutch means thatfunctions at peak efficiency even during relatively low speed operationof the chuck and even though an abnormal load is placed upon the drivenelement. It is likewise an important object to provide an improvedclutching means operable to increase its clutching action or gripon thedriven element in response to any tendency of the chuck body to overrunthe driven element.

The invention in its specific aspects aims to provide clutch meanscomprising a torsionally resilient element preferably in the form of acoil spring wound or wrapped in the direction opposite to the normaldirection of rotation of the clutch body and adapted to grip the drivenelement, the reverse winding of the torsionally resilient elementserving to increase the wrapping grip on the driven element as the chuckbody is rotated. In its other aspects the invention provides a chuck ofnovel construction that embodies relatively few operating partscompactly arranged and substantially trouble free in operation. Anotherobject of the invention is to provide a, chuck including a chuck bodyhaving a collet carried for axial movement therein and including acompression spring which urges the collet in cooperating engagement witha portion of the chuck body to compress or constrict the chuck with athreaded driving shaft in such manner that the chuck body may beadjustably positioned on such shaft to adjust the compression on theaforesaid spring.

The foregoing and other important objects and features of the inventionwill become apparent as the disclosure is more fully made in thefollowing detailed description and accompanying sheets of drawings inwhich:

Fig. 1 is a side elevational view; one-half of which is in section, ofone form of the improved automatic chuck; Fig. 2 is a transversesectional view taken on the line 2-2 of Fig. 1; Fig. 3 is a view showingthe assembly of the collet and associated collar, the view being drawnto twice the scale of that of Figs. 1 and 2; Fig. 4 is a view showingthe assembly of the clutching spring and associated collar, the scale ofthis view being the same as that of the parts in Fig. 3 Fig. 5 is a rearend elevation of the clutching spring shown in Fig. 4, the view beingdrawn to the same scale as that used in Figs. 3 and 4.

Fig. 6 is a view similar to Fig. 1 but showing a modified form of theinvention; Fig. 7 is a detailed view of the collet used in theconstruction of Fig. 6; Fig. 8 is a side view of the clutching springused in the construction of Fig. 6, the spring being shown in a scaletwice that of Fig. 6; Fig. 9 is arear view of the assembly of theclutching spring of Fig. 8 and the collet of Fig. 7, Figs. 7 and 9 beingdrawn to the same scale. Fig. 9a is a view of a modified form of springsubstitutable for. that shown in Fig. 8; Fig. 10

is a partial sectional view of a still further modified form of chuck;Fig. 11 is a transverse sectional view taken on the line ll-ll of Fig.10; Fig. 12 is a longitudinal sectional view through the chuck body ofFig. 10 Fig. 13 is a plan view of the chuck body; Fig. 14 is alongitudinal sectional view of the collet of the construction of Fig. 10Fig. 15 is a fragmentary perspective view showing the rear end portionof the collet of Fig. 14; Fig. 16 is a perspective view of one of thedriving plates of the construction shown in Fig. 10.

Fig. 17 is a partial sectional view ofanother form of the invention;Fig. 18 is a transverse sectional view taken on the line |8l8 of Fig.1'7.

Although reference herein is made to the chuck in connection with itsuse in certain instances, it should be understood that the principles ofthe invention have wider applicability. Likewise, the particularity withwhich thedetailed structures of the various modifications of theinvention in Fig. 3).

are pointed out should be taken as illustrating and not limiting theinvention.

Figs. 1, 2, 3, 4 and 5 V nut 23 is also threaded on the shaft 2! and engages the rear end of the chuck body for securing the chuck body to theshaft 2! for rotation therewith.

The chuck body includes anaxially. directed pocket in the form of anaxial bore 25, which bore may be formed entirely through the chuck bodyand may include the portion that is subsequently tapped to provide theinternalthreads i to overrun the collet 26 will cause the collet to bedriven forwardly with the result that the aforesaid wedging actionbetween the tapered portions 25 and 3% occurs to effect compression orconstriction of the forward portion of the collet on the element orspindle 28.

The chuck body 22 is provided with a sleeve or band 35 that encirclesthe chuck body about that portion thereof in whichthe screws 3d, arecarried. This band-or sleeveis-Jmounted on the chuck body 22 by a press'fit so that it is not readily displaceaole. The band 35 serves toprevent any tendency of the screws 34 to become dislodged by reason ofcentrifugal force incident to highspeed rotation of the chuck.

The'cliuck further includes within its bore 24' collar. 35 having anannular sleeve portion 3"! and anintegral annular radial flange 38. The

sleeve portion 3? fits within a counterbore 39 of that engage thethreaded dri-Ving'shaft 2%. The

frontendof the chuck b'ody22 istapered radially inwardly as at 25; for apurpose to presently appear. a v

A collet 25 is carried inthe pocket or bore 2% of the chuck body and isarranged-for limited fore and aftaxial movement therein. The collet isprovided with an axialbore 21- adapted to receive a rotatable drivenelement zdsuch as a tool or other rotatable spindle. The collet isfurther provided witha plurality of longitudinal circumferentiallyspaced slits 29 by means of which the forward portion of the collet isflexible so that it may be radially compressed orconstricted to gripthe'spindle 28. The outer periphery-ofthe forward portion of the colletis tapered as at 30 and-is'engageable'with the taper 25 of the chuckbody'bore so that movement ofthe collet axially forwardly'with respectto the chuck body resultsin a wedging relation between the taperedportions 30- and 25 for compressing or constricting the collet aboutthespindle. The construction of the chuck body and collet is such that theelement or spindle ftrnay pass completelythrough the collet and may abutthe front radial face of the driving shaft 21. V

The rear portion of thecollet is formed of a diameter substantiallylarger than the forward portion to provide a cylindrical surface 3 I.This cylindrical surface provides a pilot area by means of which thecollet is centered in the chuck body bore 24-. This surface ispreferably finished or polished so that'the collet may havefree foreand-aft axial movement in the bore 24. The rear portion of the collet isprovided'with' a pair of substantially. diametrically opposed helical orspiral slots or grooves 32 (one or" which appears These slots or groovesprovide cam tracks that extend generally circumferentially and axiallyof the collet and are cut'through that portion of the collet thatincludes the cylindrical surface 3!. Asbest shown in Fig. 2, the chuckbody 22 is provided with a pair of diainetrically opposed tapped bores33,,each of which receives a screw 34' having an integral end portionproviding a stud or follower engageable with the proximate cam track orgroove 32 in the collet 26. r

The normal direction of rotation of the chuck body by the motor shaft 2|is right-hand or clockwise asv viewed from the motor end-of'the chuck.The spiral or helical grooves or tracks 32 are cut left-hand orcounterclockwise, whereby any tendency of the rotating chuck body 22 thecollet 2t and the front face of theradial flange 38- abuts the r'ear endof the enlarged-cylindrical portion fi-l- -ofthe colle-t-a'rid'iisbrazedor-soldered thereto as ail-Ml-(Eigifdl. Itfwill-ba understood, ofcourse; that anyother-suitable method may be employed forconnectingethe: collar e'it to the collet 2B for rotation' therewith.The counterbore ia -in thecollet 25 issorhewhat" larger than the bore-21previouslydescribed-and the junction between the-bore zfi and counterbore fid'providesa shoulder Mfr- 7 The counterbore carries therewitlli-n a clutching device in the form-ofa'cei-lspring This spring abuts'at--its--rear-end against the front face of the sleeve portions?" thecollar 36 and the last-turn -of the span-gas: previded-- with a rearwardaxial projectirig portion lii whioh is received by a slot i in thesleeveportion-t't of the collar 38. Thespri-rig is connectedto:thecollar 36 for rotation therewith" by means of theprojecting portion 33',a positive corinection be tween the parts being eifected b'y means ofbraz ing or solderingasat d5 -(Fige li lt will be understood that othermeans maY-Fbe" utilized to-\ effect the connection between the spring; aandcollar 36; however. the preseiit -m ethod'yisfound to be highlyeffective. The-spring}-42 ;-has;a nominal uniform inside diameterof-asize sufiia cient to-relatively loosely receivegthe element'or spindle28, which; as aforesaid,-passes completely through the collet to'abutthe driving shaft2'i The spindle, "of course,- likewise 'pa-ssesthrough; the spring 42 and-collar 36. By this arrange-- ment thespring--42 is supported-againstradially inward distortion by the elementZEKa-ndagainsti radially outward distortion by that portion of thecollet providing the counterbore 3.,. The two coils at the forward endof the spring- G2i are slightly'reduced in inside-diameter as at 46-(Fles i and 5) to relatively tightly-grip:or establish' frictionalengagement withfthespindlefw This arrangement providesia clutchingarrangement between the spring 32 and the-spindle; The spring 42'iswoundleft-hand or-in a direction opposite to the normal dire'ctionofrotation of'the chuck body 22. Any tendency of the' chuckbody to overrunthe spindle -2$Qwillcause-' wrappingpfthe spring 12 about-thespindleg'iigso-that the' grip or clutching 'action a of the} spring i2-on-'-thespindle is increasedi It wilbtlius be-seen -thati the spindleZB willnot slip in thechuck eventhough it isoperatedunderoverload-conditions.

' A second coil spring Al of a size substantially larger than thespring-112 surroundsthe rearpor tionof thejspindle 28-andispla undercomfpr'ess'ion' between the front radial face of the motor shaft 2| andthe rear radial face of. the flange 38 on the collar 36. This spring,although relatively light, tends to urge the collet 26 forwardly so thatthe tapered front end portion iiil thereof engages the inside taper onthe bore 24 of the chuck body 22. The bore 21 of the collet is providedat its extreme forward end with an outwardlytapering or countersunkportion 48 by means of which insertion of the spindle into the chuck isfacilitated. When the parts of the chuck are at rest, the tendency ofthe collet 25 will be to assume a neutral position with respect to therelationship between the cam tracks 32 and follower screws or studs 34,except insofar as the collet is urged forwardly by extension of thecompression spring 41. Because of the tapered portion 48 at the frontend of the collet bore 21, the spindle 28 may be easily inserted intothe collet. The action of inserting the spindle 23 will tend to move thecollet rearwardly and relieve the wedging action of the tapered surface25 thereon, thus further facilitating insertion of the spindle. Thecoils of the clutching spring 42 normally lie one against the other andno difficulty is experienced in moving the spindle 28 axially rearwardlythrough this spring, inasmuch as the rearend of the spring abuts thefront of the collar 86 and the collar is in turn abutted by thecompression spring 41.

When the spindle 28 iswithdrawn from the chuck, there is no undueelongation of the spring 42 caused by frictional drag of the reducedcoils 46 thereof on the. sprindle 28, inasmuch as the front coil of thespring may abut the shoulder 4| formed at the junction of the bore 21and counterbore 39. The shoulder 4| thus serves tostrip the spring 42from the spindle 28 as the spindle is withdrawn from the chuck.

Since the chuck body 22 is adjustably positionable on the motor shaft2|,and since the spring 41 abuts the front end of the motor shaft,compression on the spring '41 may be varied by adjusting the chuck bodyon the shaft and the adjusted position of the chuck body may be securedby means of the lock nut 23.

Figs. 6, 7, 8 and 9 The chuck construction of this modified form of theinvention is similar in some respects to that previously described. Forthe purpose of simplicity in the description, the chuck will bedescribed in connection with its use with a motor or driving shaft ofthe type shown in Fig. 1 and the same reference character 2| will beused to designate the shaft. The chuck body is shown at 50 as having anaxial pocket or bore 5| the rear end of which is internally threaded toreceive the driving shaft 2|. The lock nut 23 is associated with theshaft and chuck body 50 in the same manner that the corresponding partsare associated in Fig. 1. The chuck body further includes a plurality oflongitudinally extending slots 52 (only one of which is shown in Fig. 6)opening radially outwardly from the axial bore 5|. The forward end ofthe bore 5| is radially inwardly tapered as at 53. A collet 54, shown indetail in Fig. '7, is carried in the bore 5| for limited fore and aftaxial movement with respect to the chuckbody 50. The collet has an axialbore '55 for receiving the rotatable driven element 28 and at itsforward end is longitudinally split as at 56 so that its flexible endmay be radially compressed or constricted to grip the element 28. Theforward portion ofthe collet is provided with an external taper 51 whichcooperates with the 6 internal taper 53 of the chuck body bore 5| toaccomplish a wedging action-on thecollet when the collet is movedaxially forwardlyin the chuck body 50. The rear end portion.;of thecollet includes a portion of increased diameter to provide acylindricalsurface 58 which is associated with the chuck body bore 5|for the. purpose of centering and pilotingthe collet in the chuck body,the arrangement being similar to theconstruction of Fig. l. The enlargedcylindrical portion 58 of the collet is provided with a pair ofdiametrically opposed radial bores 59 (only one of which is shown) whichare generallyiin radial alignment with the slots 52 in. the chuck body50. A band axially slidablyencirclesthatportion of the chuck body 50 inwhich theslots .52 are formed. This band is provided with apair ofdiametrically opposed tapped bores (only one of which is shown) and eachbore carries a screw 6| having a radially inwardly extending studportion 62 whichenters the proximate bore or opening 59 in the collet'54. By means. of theconstruction thus far described, the collet 54,together with the band 60, may have limited fore and. aft movement withrespect to the chuck body, the slots 52 in the chuck body. beingsufficiently long to permit this movement. A compression spring 53 is.interposed between the front radial face of the motor shaft 2| and therear of the collet 54. The function of the spring is to urge the collet54 normally axially forwardly so that the wedging action between thetapers 53 and 51 is accomplished. The band 68 carries a sleeve 54, theforward portion ofwhich is tapered at 65 and spun onto a complementarytaper on the forward end of the band 60. The sleeve 64receives the band60 in a press fit so that the two parts may move axially together. Therear portion of the sleeve 64 is enlarged at E6 to provide a portionadapted to be gripped by an operator for moving the band 50 and collet54 rearwardly against compression of the spring 63, so that the forwardportion of the colletis released from the taper 53 of the chuck bodybore 5| to release the gripof the collet on the element 28, thuspermitting withdrawal of the element.

The chuck further includes a driving device or clutch between the collet54 and rotatable element 28. This device takes coil spring 81constructed very much like the coil. spring of the chuck of .Figs. 1 to5. The spring 6'! is shown by itself in Fig. 8. The front two turns orcoils of the spring 5'! are reduced in inside diameter to relativelytightly receive the rotatable element 28. The spring 61 encircles theelement 28 within a-counterbore 58 formed in the collet 54. Thecounterbore is somewhat larger than the bore 55 and ashould er 59 isformed at the junction thereof with the bore. The rear end of the spring31 includes a tangential projection 10 which is received in a slot 1|formed in the enlarged cylindrical portion 58 of the collet. Thisprojection may be soldered or brazed as at 12 (Fig. 9) tothe collet. Thespring, encircling the inner or rear end of the driven element 28, issupported thereon against distortion radially inwardly and is supportedagainst radially outward distortion by means of belilngD confined withinthe counterbore 6B of the co e The coils of thespring 67 are woundleft-hand or in the direction opposite to the normal direction ofrotation of the chuck body 50. The collet 54 is connected to the chuckbody 50 for rotation therewith by means of the screws 5| which the formhere of a engage the chuck body along theportions thereof Since thespring" B'Lis that border theslots 52; connected to the collet 54. bymeans 10f the pro e'crtion 19, the springgwill tend'to rotate with thecollet and any tendency ofthe chuckfb'ody Bllto overrun the drivenelement.2B will cause the means of adjusting the chuck bodytfl on thethreaded motor shaft 21' and securingthis :position by means of the locknut 23, as in the construction of Fig. 1. Howevenwhereasthe spring i! ofFig. I is relatively light and gripping engagement of the collet 26on'the element 28= depends in partupon the axial iorward move ment ofthe collet 26 by means ofthe spiral tracks 32 and followers and in parton the clutchingaction of the clutch spring 42; the compression spring63 of Fig. 6'is relatively stronger; inas much as the latter spring-mustservein part as the means for driving the collet-54 axially forwardlysothat the wedging action between the tapers 53 and 51 accomplishescompression or constriction of the collet 5 2 onthe element 28.-

The shoulder 69 at the junction'of' the bore 55 and counterbore 68in thecollet '5 l' serves to engage the spring '61 to strip thespring from theelement fit as the element is withdrawn from the chuck. V

The sleeve fi l'on theband E9 servestoretain the screws tilagainstradial displacementincident to rotation of the '-chuck.-" be polished orotherwisefinished to furnish-a de sirable exterior appearance to thechuck.- V V This view showsia modified form of clutch spring .t'icorresp'ondingto the spring 'li'l but having. the next to the lastentrance-end turn reducedin diameter instead of' the last-tw turns. Thisfacilitates. insertion ofthe -tool' shank because of the large diameterlast turn serves as a centering guide io'r the-inserted'end of the-tool:

The chuck comprising:this-modifieddorm ol the invention includes; achuckbody 86 provided atone end with an internally threaded bore-tl by meansof which thechucli body may be carried on the motor shaft 2 i. The.chuck body'further includes an intermediate; pocket 82 which opensradially outwardly atfdiametri'c'ally' opposed portions of the chuckbody: The forward external surface of the chuck body isltaperedforwardlyas at 83 and this portioni's-provided with an axial bore 84 coaxial withthe'internally threaded bore 8 I. The rear portionzof the chuclc plishedbetween the internal taper 86 of the bore:

84; and an external taper 8% at theforward .end of the collet. Thecollet is provided withan axial bore QEi and an enlarged counterboreill... The bore 99 receives the rotatable element 28; which element maybe inserted through the bore-1911 This sleeve-may and through thecounterbore 9| of the collet-suificiently far into the chuckxuntil therear end of the element encounters the frontradial iaceiof themotorshaft 2L. Aclutching device-in the form of a coil spring 92.: iscarried'withinthe counterboreei of the collet 81 and encircles therotatable elementZil; This spring,.like thesprings t2 and 5? of Figs. 1and 6 respectively; ha'sits front two coils .formed of reduced insidediameter.

to effect a clutching 0r gripping actiononthe element 28:.

large to relatively. loosely permit the elementx28 to pass therethrough.

The rear end of the collet 8? is providedwith' a pair of axiallyrearwardly extending portions'inthe form of. driving lugs 93; one. ofwhich is slotted at 9 The rear end of the spring '92'may include aprojection onthe order of that formed on the springtl of Fig: 6. Thisprojection may engage the slot 94 in onedriving lug 93 to connectthespring to the collet for rotation therewith. This specific connectionof thespr-ing. 92 t the collet 87 has not been shown; inasmuch as it'maybe readily understood from a description of what has been. describedbefore. Bymeansthatwill be hereinafter described, the colletBlisconnected to the chuck'body 88 for rotation there'- with. The springQ2, like the springs'dli' and Gi previously described, is Woundleft-handor in the direction opposite to the normal direction of rotation of thechuck body so that any tendency of the chuck. body tooverrun the element28 will serve to increase the grip of. the spring. 92" on the element. V

The shoulder provided: at the junction of the bore iii and counterbore9| ofthe colletfil pro vides means for engagingth'e spring 92 130. stripcally of the chuck body ltflso that-opposite ends thereof" extendradially through opposite sides of the pocket whereby the endportions ofthe-flat side's et engage i11 driving-relation with those portions ofthe chuck bodybordering on the'poelcet The member S5=iscentra1lyapertured at il'l so that the rear end portion of the driving element 23may pas therethrough (Fig. 10 The aperture i-l'i is considerably largerthan the element-is and receives a bushing 98'." This bushing includes asleeve portion that is=received in apress fit'by the. aperture -91 'sothatthe memberi ii and bushing 98 are constrained for rotation. andaxial movementtogether. The forward ifaceoi thev sleeve portionof the.bushing 98- serves also asineans against which'ther'earend of theolutchspring 32' may. abut. The inside: diameter of: the boreiinthebushing t-is such asto reeeive' theelement I28 in a sliding fit andthus serves .as means. foradditionally centeringand supporting theelement; The supporting relationship betweenlthe element and the-bushingis mutual, inasmuch. as the latter i supported on the formeniand. stillfurtherserves to center and retain the. drive member 95.

The rear .portionof the bushing 9 8 is provided- The remaining. coils ofthe spring. are. of. a. nominal uniformidiameter sufficiently with arearwardly and inwardly tapering face 99. Each of the oppositeends ofthe rear portion of the drive member 95 is provided with a rearwardlyand outwardly tapering surface or cam face I00. 'A second drive memberIOI is positioned in the chuck body adjacent the rear end of the slot orpocket 82. This member is apertured at I02 to receive the element 28 ina sliding fit and is further provided with a diametrically extendingraceway I03. A pair of centrifugal weights in the form of balls I04 iscarried in the raceway I03, the balls being'normally separated by thetapered face 99 on the bushing 98, the balls being further disposed between the raceway I03 and the cam faces I on the drive member 95.

The relationship of the parts is such that rotation of the chuck willcause the balls I04 to move radially outwardly in response tocentrifugal force. Outward movement of the balls, by virtue ofengagement with the cam faces use on the drive member 95 will cause thedrive member 95 to move axially forwardly or to the left as viewed inFig- 10.. t This movement of the member 95 will effect forward axialmovement of the collet 61 and will function to increase the grip of thecollet on. the element 28 by means of the constriction or compression ofthe forward end of the collet as the tapering surface 89 of thecollet iswedged into'the taper 86 of r the chuck body bore 84. "It will thus beseen that the grip of the collet 8'! on the element 28 is in directproportion to the speed of rotation of the chuck. Even though the gripof the collet 8'! on the element 28 tends to relax during low speedoperation of the chuck or during such times as the element 20 isoverloaded, the clutch spring 92 will maintain driving connectionbetween the chuck body 80 and the element.

The exterior of the chuck body is finished by a sleeve or thimble I05which is tapered forwardly to correspond with the forward taper 83 onthe chuck body. The rear end portionof the sleeve I05 is spun over anannular flange I06 on the chuck body as at I01. The sleeve I05 is thussecured to the chuck body 80 as effectively as if formed as a partthereof. The sleeve or thimble may be polished or otherwise finished tolend to the appearance of the assembled chuck.

Figs. 17 and 18 This form of the invention eliminates the collet andsubstitutes therefor, as a centering means for the tool shank 28, anannular guide member II I having a pilot bore II2 with a flared entranceH3. Guide member III has an annular flange I I4 clamped between a flangeH5 on a retaining cap H6 and the front or left end of a centrally boredbody 1.

Body III, in addition to being threaded at I I8 for attachment of thecap I I6, is also internally threaded at II9 for attachment to apower-driven member as the armature shaft 2! in Figs. 1 and 6. A largediameter portion I2I of the bore in the body II I provides a chamber fora helical clutch spring I22. The left end I 23 of this spring is turnedradially outwardly into a notch I24 in the end of the body II! as ananchorage and for causing rotational force to be imparted to this endof. the spring; see Fig. 18. The opposite end of the spring has areduced diameter convolution I25 for initially gripping the tool shankas the latter is inserted therethrough into a pilot portion I26 of thebody bore. A shoulder I21 between the bore portions I 2| and I26 isabutted by the convolution I25,

10 pursuant to forcing the end of the tool shank therethrough, andthereby prevents inordinate elongation of the spring while permittingexpansion of such convolution. The direction of winding of the clutchspring is such that initial overrun of the device with respectto thetool shank will cause the spring convolutions to progressively grip theshank and ultimately establish a positive driving connection therewith.Inasmuch as the clutch spring convolutions between its anchored end andthe reduced diameter convolutions will necessarily embrace the toolshank before these convolutions can be tightened, there is assurancethat no partially inserted tool can initiate a contractual winding ofunsupported convolutions with possible inordinate contraction and.injury thereto.

In the other embodiments of the invention the jaws of the collet havethe prime function of piloting the tool while the clutch springconstitutes the primary driving coupling for the tool. Although thecollet jaws engage the tool for piloting at only one end of the clutchspring, the piloting function is well executed because of the jawsgripping the tool,- i. e., there is no radial clearance between the tooland the pilot means. The absence of a gripping pilot means iscompensated for in the present embodiment by the presence of the twocomplemental pilot means components H2 and I26 at opposite ends of theclutch spring.

In conclusion The operation of each of the chucks disclosed herein hasbeen set forth in connection with the foregoing description. It will beseen that in each form of the invention the improved chuck ischaracterized by means tending to eliminate any slippage between thechuck body' and the driven element 28. In the form of the inventionshown in Fig. l the'clutch spring 42 serves in large part to establishthe driving relationship between the chuck body and driven element. Inaddition, the grip of the collet 26 on the element 28 is increased bymeans of the spiral tracks 32 and followers 34 which function inresponse to any tendency of the chuck body to overrun the collet 'andelement. In the chucks of Fig. 6 the clutching spring may operate inconjunction with the compression spring 63. In the chuck of Fig. 10, theclutch spring operates in conjunction with centrifugal force meansoperable in response to rotation of the chuck.

Other features of the invention will undoubtedly occur to those skilledin the art, as will various modifications and alterations in theconstruction of the preferred forms of the invention herein illustratedand described. It should be understood, of course, that suchmodifications and alterations may be made without departing from thefundamental principles of the invention and it is not desired that theinvention be delimited by the exact structural forms set forth.

What is claimed is:

1. A driving member for connecting a chuck and a coaxial cylindricalrotatable element, comprising: a coil spring having a nominal insidediameter of such uniform size throughout a substantial axial lengththereof as to loosely receive such element coaxially therein andincluding at one end thereof a portion of reduced inside diameter forrelatively tightly receiving the element, and at the other end a portionadapted to be connected to a chuck in driving relation thereto.

2. A driving member. for connecting a chuc and a coaxialncylindricalrotatable element, cornprising: ,a coilrspringjiavinga majority of its;co ils of a nominal uniform inside diameter of such size'as torelatively loosely receive such, element coaxially therein and havingcertain of its coils at 'one end thereof reduced in inside diameterforrelatively tightly gripping the element, the other. endoi theispringincluding a portion adapted to be connected to a chuck in drivingrelation thereto. v

3.; A driving member foiyconnecting a chuck andacoaxialcylindrical-rotatable element, comprising: .a coil (spring ,havingaimajoritypf its coils of a nominal uniform inside diameter of suchsizeasto relatively loosely-receive such element coaxiallythereinpandrhaving certain of its coils at one end thereof reduced ininside diameter for relatively tightly gripping the element, thelast-coilat the other end of thespring includingna proj ecting. portionadapted ,to be connected to a chuckvin driving relation thereto,

a l. A.-.drivingrmember for connecting-a rotatable body with acylindricalzelement to -bedriven coaxiallywithsuch body, comprising: acoil 7 spring having majority of its coils of a nominal. uniforminside,diameter such as to loosely receive theelement when it: isinserted-endwise throughan entrance endl of such spring, andtherezbei-ng alzportion ofthe coils spaced from lsuchentranceend and ofdiminished diameter to initially grip onto the tool after it has enteredsuch end and projected through said majority of coils.

5. In a driving chuck for a tool, a chuckbody having an axial borereceivable of a shankof such tool, said bore having a clutch-receiving.portion and a more inward portion of less diameter' for piloting thetool shank and forming a shoulder between the bore portions, a helicalclutchelement in the clutch-receiving portion of the bore to axiallyreceive the tool shank, the outer end of the clutch elementbeinglanchored for rotation with the chuck body while a more inwardportion of such element is reduced in diameter to initially gripthe toolshank and an intermediate portion of the element comprises coils ofequal internal diameter for receiving the tool shank but beingprogressively grippable lthereonlin driving relation pursuant to aninitial.,rotati,on :of the reduced diameter portion with the toolrelativelyto the chuck body, and

the inner endof the clutch element being adjacently to said shoulder forabutment thereagainst to prevent elongation of the element by the toolshank= as it iszprojected therethroug-h toward the pilot bore portion.

n6. Ina drivingchuck for a tool, a chuck body having an axial lborereceivable of a shank of such toolfsaid bore having inner and outer tool.shank pilot zportions and a clutch-receiving portion-between said pilot-portions, the clutch-receiving portion being of :greater diameter thanthe inner pilotportion to receive a helical clutch element and forming ashoulder at, the inner end of said clutchereceiving:portion, the outerend of the :clutch-element being anchored for rotationwi-thjthepchuck:bOdYWhile a more inward portion ofysujch:elementpisreduced. in diameterto initiallyrgriythetool shank and an intermediate portioniof theelement comprises coils of equal internal diameter 'for receiving thetool shank but; being progressively grippable thereon in drivingrelation pursuant to an'initial rotation ofthe; reduced diameter portionwith the tool relatively-to the. chuckb0dy,and the inner end of theclutchelezn'entbeing adj acently to said shoulderforabutmentVthereagainst to prevent elongation oflthe. element by thetool shank as it is projected;therethrough toward the inner pilotportion ofthe bore.

OSCAR H. BANKER.

REFERENCES CITED Thegfollowing references-are of record in the file vofvthis ,patent:

-UNITED' STATES PATENTS

